ESR-MRI Using Low-Temperature Magnetic Resonance Force Microscopy

The low-temperature operation of Magnetic Resonance Force Microscopy (MRFM) leads to a significantly better signal-to-noise ratio (SNR) than at room temperature, because of an increase of the spin magnetization and a reduction of the thermo-mechanical noise of the cantilever. We have built a low-temperature equipment, which is capable of operating in vacuum at liquid helium temperature. Our setup employed the sample-on-cantilever design at present. A magnetic needle with $100~{\rm \mu m}$ in diameter was placed on a stage to generate magnetic field gradient $11.3~{\rm G/\mu m}$ at the magnetic field $714~{\rm G}$. The 3D closed-loop stage based on slip-stick principle allows a $200 \times 200 \times 200~{\mu m}^3$ scan range with $50~{\rm nm}$ resolution. The experimental results of the 2D magnetic resonance force map carried out on diphenylpicrylhydrazil (DPPH) at $T = 14~{\rm K}$ are shown and an improvement of the SNR by 154 compared with the results at room temperature is confirmed. The 2D reconstructed images will be shown as well.